Field of the Disclosure
The present invention relates to an organic light emitting display (OLED) device capable of preventing a pile-up problem and a manufacturing method thereof.
Description of the Related Art
Flat display devices having a thin profile, light weight, low power consumption and high display quality include a liquid crystal display (LCD) device, a plasma display panel (PDP) and an OLED device. The OLED device is self-emitting and does not require an additional light source. As a result, the OLED device can be thinner and lighter weight and have a faster response time, improved color reproduction, lower power consumption, improved viewing angle, etc. Generally, the OLED device is manufactured by a dry process such as a vapor deposition. However, a wet process such as inkjet printing can be used to fabricate an OLED device having an increased size.
FIGS. 1A and 1B are schematic cross-section views illustrating a manufacturing process of the OLED device according to related art.
Referring to FIG. 1A, a lower electrode 13 is formed on a planarization layer 11, which can be formed to cover a thin film transistor for driving an OLED device, and a bank layer 12 is formed on peripheries of the lower electrode 13. A center of the lower electrode 13 is exposed through an opening of the bank layer 12.
Referring to FIG. 1B, an organic emitting layer 14 is formed on the lower electrode 13. The organic emitting layer 14 contacts the lower electrode 13 though the opening of the bank layer 12. When the organic emitting layer 14 is formed by a wet process, a pile-up problem is generated in the organic emitting layer 14. Namely, a center of the organic emitting layer 14 has a thickness that is different than a thickness of the peripheries of the organic emitting layer 14. In particular, a solvent in a solution for the organic emitting layer 14 is evaporated at peripheries of the lower electrode 13 before a solvent in a solution for the organic emitting layer 14 at the center of the lower electrode 13 due to a Coffee-Ring effect, which causes the organic emitting material to move toward the peripheries of the lower electrode 13 via surface tension. As result, peripheries of the organic emitting layer 14 are thicker than a center of the organic emitting layer 14.
Next, FIGS. 2A and 2B are a cross-sectional view and flow chart illustrating another OLED device according to related art.
Referring to FIGS. 2A and 2B, the OLED device includes a double-layered bank layer. Namely, a bank layer including a lower bank layer 22 and an upper bank layer 23 is formed on the peripheries of the lower electrode 24 on the planarization layer 21. The lower electrode 24 as an anode, for example, may be formed of indium-tin-oxide (ITO), and an organic emitting layer, which includes a hole injection layer (HIL), a hole transporting layer (HTL), an emitting material layer (EML) etc., may be formed on the lower electrode 24. The OLED device including the lower electrode 24 as an anode formed of ITO, and the organic emitting layer formed on the lower electrode 24, may include the lower bank layer 22 formed of a hydrophilic material, and the upper bank layer 23 formed of a hydrophobic material. However, the OLED device including the double-layered bank layer has is limited due to a decreased size of the emitting area resulting from a process margin for overlapping the lower electrode 24, the lower bank layer 22 and the upper bank layer 23.